jmgimeno

(defn bfc
  [program]
  (let [allowed #{\+ \- \< \> \[ \] \.}
        src (->> program (filter allowed)
                 (interpose \space) (apply str))
        fns (zipmap '(- + < > . ?) (repeatedly gensym))]
    (letfn [(bfc* [s]
              (if (vector? s)
                `(while (not (~(fns '?))) ~@(map bfc* s))
                `(~(fns s))))]

jboner

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD

cgrand

;; I could have used a closed dispatch (aka cond) but you may find this version more enjoyable
;; the spec format is the one provided by BG

(defprotocol Selector
  (-select [s m]))

(defn select [m selectors-coll]
  (reduce conj {} (map #(-select % m) selectors-coll)))

(extend-protocol Selector

stuarthalloway

// Datomic example code

package datomic.examples;

import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

import static datomic.Peer.*;

stuarthalloway

;; Datomic example code
(use '[datomic.api :only (db q) :as d])

;; ?answer binds a scalar
(q '[:find ?answer :in ?answer]
   42)

;; of course you can bind more than one of anything
(q '[:find ?last ?first :in ?last ?first]
   "Doe" "John")

svs

So I don't have a model called Person, but I use hashes like {:name => "Siddharth", :sex => "Y"}. Great. Now I want to validate the presence of certain fields before persisting to the database. What do I do?

Module PersonValidation
  function validate_presence_of_name(person_hash)
    person_hash[:errors][:name] = "EEENKKK!" unless person_hash[:name]
  end
  
  ...
 ...

redinger

Setting up Emacs daemon on OS X

Tired of waiting for emacs to start on OS X? This step by step guide will teach you how to install the latest version of emacs and configure it to start in the background (daemon mode) and use emacsclient as your main editor.

Install Cocoa Emacs

Download the latest pretest version of [Emacs for Mac OS X]: http://emacsformacosx.com/builds

nathanmarz

;; Determine if any of the causes of the exception was of the specified type
(defn exception-cause? [klass ^Throwable t]
  (->> (iterate #(.getCause ^Throwable %) t)
       (take-while identity)
       (some (partial instance? klass))
       boolean))

alandipert

(defn isbn13? [isbn13]
  (let [nums (map #(Integer/parseInt %) (re-seq #"\d" isbn13))
        first-nums (butlast nums)
        sum (->> first-nums
                 (map vector (cycle [1 3]))
                 (map (partial apply *))
                 (reduce +))        
        last-num (last nums)]
    (= last-num
       (-  10 (mod sum 10)))))

cs224

;;; implementation in clojure of the levenshtein allison algorithm as defined here:
;;; http://www.csse.monash.edu.au/~lloyd/tildeFP/Haskell/1998/Edit01/

(defn min3 [w nw n]
  (if (< w nw) w (min nw n)))

(defn generate-diagonale [a b nw fn-diag-above fn-diag-below start]
  (if start
    (lazy-cat (list nw) (generate-diagonale a b nw fn-diag-above fn-diag-below false))
    (if (or (empty? a) (empty? b)) '()